package alg.leetcode;

/**
 * 判断环形链表
 */
public class No46 {
    static class ListNode {
        int val;
        ListNode next;
        ListNode(int x) { val = x; }
    }
    public boolean hasCycle(ListNode head) {
        if (head==null||head.next==null) return false;
        ListNode slow = head;
        ListNode fast = head.next;
        while (slow!=fast) {
            if (fast==null||fast.next==null) return false;
            slow = slow.next;
            fast = fast.next.next;
        }
        return true;
    }
}
